Caption: Cancer drug acting on a leukaemia enzyme. Molecular models of two views of an enzyme involved in leukaemia being affected by a drug. In both views (lower left and upper right) the molecular structure of the enzyme is depicted in tubular form (faded colours) and the enzyme's shape (secondary structure) by helices and arrowed sheets (solid colours). The drug is a small molecule, here shown in tubular form (red), best seen at lower left, but also at upper right. Its presence prevents the enzyme's function in the cellular processes of leukaemia (blood cell cancer). This enzyme is C-Abl kinase from a mouse. The drug is Imatinib, also known as STI-571.